Load control apparatus for cranes

ABSTRACT

Apparatus for preventing the tipping over of cranes which includes a loading beam positioned colinear with the line extending from the hinge point of the boom to the anchor point of the boom support means, one end of the beam being connected to the frame, the other end of the beam constituting the anchor point, and means responsive to the deflection of the anchor end of the beam for limiting the tilting moment of the crane.

United States Patent 72 Inventor Alvin H. Wilkinson Tillala, Okla. [2l|Appl. No. 846,387 [22] Filed July 31, I969 [45] Patented Oct. 12, I971[7 3] Assignee Auto Crane Company Tulsa, Okla.

[54] LOAD CONTROL APPARATUS FOR CRANES 2 Claims, 6 Drawing Figs.

[52] U.S. Cl 212/39 MS, 2l2/39 B, 2l2/39 [51] int. Cl B66c 13/50 [50]Field otSearch 2l2/39,39 B, 39 MG, 39 l l References Cited UNITED STATESPATENTS 3,072,264 l/l963 Sennebogen 2l2/39 MS 3,200,963 8/1965 Vermes 2I 2/39 MS FORElGN PATENTS 562,004 ll/l957 Belgium 2l2/39 [149,974 ll/l960 France 212/39 B l,l39,257 ll/l962 Germany... 2l2/39 [255,263ll/l967 Germany 2l2/39 Primary Examiner-Harvey Cv Hornsby Assirtan!ExaminerMerle F. Maflei Attorney-william S. Dorman PATENTEnncnzrsn3,612,294 SHEET 10F 2 2000 LBS FIG. I

ALVIN H. WILKINSON INVENTOR ATTORNEY PATENTEU UUIZIQTI 3812294 SHEET 2BF 2 ALVIN H WILKINSON INVENTOR ATTORNE Y LOAD CONTROL APPARATUS FORCRANES The present invention relates to a safety device for preventingthe tipping over of cranes or the like. More particularly, thisinvention involves means for sensing the pitching or tilting moment withmeans for preventing a further increase in the tilting moment beyond apredetermined value thereof.

The desirability of preventing cranes or the like from tipping over iswell recognized. To this end, it is conventional to provide hoistingequipment with means for measuring the pitching moment with furthermeans to prevent the pitching moment from exceeding a predeterminedvalue as soon as that value is reached. However, the prior art teachesthe use of rather complicated devices to accomplish this purpose. Aswill hereinafter appear, the present invention represents a simpler andmore accurate method of determining and controlling the pitching moment.

Briefly stated, the present invention should be considered in terms of acrane having a boom pivotally supported thereon at what will bedetermined as a hinge point; a boom support means which is variable inlength and which can be a cable or hydraulic cylinders will connect atits upper end to the free or crown end of the boom. The other end of theboom support means will connect to an anchor point on the superstructureof the crane. The hinge point, the crown point and the anchor point forma triangle. The plane of this triangle is a vertical plane in which theboom moves. In one form of the invention, a cantilever beam is locatedat the anchor point and, in fact, the free end of this cantilever beamactually becomes the anchor point. The beam is connected to thesuperstructure in such a manner that its longitudinal axis is colinearwith the line connecting from the hinge point to the anchor point; byplacing an electrical switch adjacent the anchor point and/or cantileverbeam and by causing this switch to open or close, depending upon thedeflection at the end of the beam, the tilting moment can be limited. Inanother form of the invention, the beam is pivotally connected to thesuperstructure of the crane but its longitudinal axis still falls alongthe line connecting between the hinge point and the anchor point; at theanchor point the beam is connected to one part of a hydraulicpistoncylinder combination and the other portion of the pistoncylindercombination is secured to the superstructure; in this instance, thedeflection at the anchor point end of the beam will cause a change inhydraulic pressure within the pistoncylinder combination which can beused to control the tilting moment.

It is a principal object of the present invention to provide a safetydevice to prevent the tilting moment on a crane or the like fromexceeding a predetemiined value.

It is another object of the present invention to provide a safety deviceof the type referred to above which includes a rigid beam disposed alonga line connecting between the hinge point and the anchor point, theouter end of the beam constituting the anchor point, with meansresponsive to the deflection of the anchor point end of the beam forlimiting the tilting moment.

It is a further object of the present invention to provide a safetydevice of the type referred to above wherein the rigid beam is acantilever beam, the free end of which is the anchor point withelectrical switch means disposed adjacent the anchor point end of thebeam for limiting the tilting moment.

It is a further object of the present invention to provide a safetydevice of the type referred to above which includes an additional safetymeans to prevent structural overload.

It is still a further object of the present invention to provide asafety device of the type referred to above wherein the rigid beam ispivotally connected to the superstructure wherein the other end of thebeam is the anchor point, the anchor point being connected to one end ofa piston-cylinder hydraulic unit, the other end of the hydraulic unitbeing connected to the superstructure with means responsive to theincrease in pressure within the hydraulic unit as a result of thedeflection of the anchor point end of the beam to limit the tiltingmoment.

Other and further objects and advantageous features of the presentinvention will hereinafter more fully appear in connection with adetailed description of the drawings in which;

FIG. I is a semidiagrammatic view of a hoisting apparatus having apivotal boom;

FIG. 2 is a diagram showing the plane of movement of the boom of FIG. 1with respect to the hinge point and the anchor point;

FIG. 3 is a moment diagram;

FIG. 4 is an elevation of one fonn of a sensing and control device madein accordance with one embodiment of the present invention;

FIG. 5 is an end view of the switch and associated beam structure shownin FIG. 4; and

FIG. 6 shows a safety device which is a modified form of the presentinvention.

Referring to the drawings in detail, FIG. I shows a crane carrier 10having a boom 11 connected to the superstructure of the apparatus atpoint H" which will sometimes hereinafter be referred to as the hingepoint. A boom support means 12, which is of variable length and whichcan constitute cables or hydraulic cylinders, connects from the upperend of the boom at point C" which will sometimes hereinafler be referredto as the crown point. The lower end of the boom support means 12connects with the superstructure at point A" which will sometimeshereinafter be referred to as the anchor point. The center of gravity ofthe entire unit is indicated by the reference character "G" to provideadditional stability, outriggers 13 are included.

As the boom support means 12 is shortened with relation to the diagramshown in FIG. 1, the boom 11 will be lifted to a more vertical position;conversely, as the boom support means is relatively lengthened, the boomII will be lowered to a more horizontal position with respect to FIG. 1.Details of the boom support means are not shown; in the event that theboom support means were a cable, a pulley or pulleys could be located onthe crown end of the boom with an additional line (not shown) leading toa winch (not shown) mounted on the superstructure for varying the lengthof the boom support means 12. In the event that the boom support means12 were hydraulic cylinders, obviously, hydraulic controls would beprovided to permit an increase or decrease in the length of the boomsupport means.

In order to support a load from the end of the boom ll, there isprovided a hook 14 which is connected to the outer end of a cable 15.The cable 15 passes around a pulley (not shown) located at the crown endof the boom 11 and a line leads from this pulley to a winch (not shown)on the hoisting apparatus for winding in or letting out the cable 15 andlifting or lowering the hook 14.

The hinge point H, the crown point C and the anchor point A form atriangle structure H-C-A commonly referred to as a truss. As the planeis passed through the points H-C-A, there results a vertical plane (seenow FIG. 2) in which the segment of the truss H-A is fixed as to lengthand position while the boom structure 11 can rotate about the hingepoint H between points "B" and D, for example. The support means 12 asindicated heretofore, will be of variable length.

The line segments A-H and I-l-D of FIG. 2 are used to form the momentdiagram of FIG. 3. If the distance between points A and H is consideredto be 5 feet, and if the extension of the cable 15 were to intersect theline H-D 5 feet to the right of point II, a load of 4,000 pounds on thehook I4 would be compensated by a load of 4,000 points at point A normalto the line A-H because the opposite moments would be 20,000 footpounds. If this tilting moment of 20,000 foot pounds was considered tobe the desired maximum tilting moment, the boom loading can bedetermined for other dispositions of the boom. For example, as shown inFIG. 3, the safe load would be 2,000 pounds at a 10 foot reach and L000pounds at a 20 foot reach. Thus, with a sensor at point A to limit theforce to 4,000 pounds in a direction normal to line A-H, the proper boomloading can be insured regardless of the angle of the boom 11.

FIG. 4 shows a specific sensor and mounting means for the anchor point.A rigid beam 16 is supported on the superstructure of the crane carrierI as a cantilever beam by rigidly fixing the lower end 17 to a portion18 of the superstructure by means of the bolt 19 or any other suitablemeans. The free end of the beam 16 is connected to a toggle member 20which forms the lower end of the boom support 12 by means of the anchorpin A-l, the center of which is located at the anchor point A. A switch21 is mounted on the superstructure in any convenient manner (not shown)and is positioned adjacent the anchor point end of the beam 16 such thatmovement of the anchor point end of the beam will cause the switch toopen, as will hereinafter appear, when the load on the beam 16 exceeds apredetermined value. In the switch, element 22 is a grounded terminal,contact 23 is mounted on the outer end of a spring arm 24 so that in theclosed position as shown, the contact 23 bears against the groundedterminal 22. The other end of the spring arm 24 is connected to aterminal post 25 which in turn connects with aconductor 26 leading to amotor or other control circuit (not shown). The switch 21 is alsoprovided with an outer lever arm 27 which is pivotally mountedinternally of the switch at 28 and which is provided with a pin 29 whichholds the spring arm 24 in the position shown. A screw 30 is threadedthrough the beam 16 and contacts the outer lever arm 27. This screw 30can be adjusted so that the contact 23 will open when a predeterminedforce due to boom loading is reached.

It should be understood that the longitudinal centerline of the beam 16falls along the line between points A and H. Thus, assuming a desiredmaximum boom loading of 20,000 foot pounds and, regardless of the angleof inclination of the boom 11, if the resulting force in the direction Ron FIG. 4 exceeds 4,000 lbs., the deflection of the beam 16 would besufficient to open the contact 23 and interrupt the circuit between theconductor 26 and the ground.

The outer end of the toggle 20 is provided with an adjusting screw 31for a purpose which will hereinafter appear. In cases where the hook 14were disposed to the left of the right-hand outrigger support 13, thetilting moments would be negative in value. Therefore, the crane couldlift loads restricted to the structural strength of the crane withoutdanger of tilting. To provide for this greater load, the adjusting screw31 is incorporated in the toggle 20 so that in the dotted line positionof the toggle 20 shown in FIG. 4, the screw 31 will contact the switchlever arm 27 and push it to the left so that a greater deflection of thebeam 16 will be required to open contacts 23. The screw 31 can beadjusted so that the contact 23 will open before the safe structuralload was exceeded.

In the embodiment shown in FIG. 6, the rigid arm 33 is not cantileversupported as in the case of FIG. 4. The arm 33 is pivotally connected toa portion 34 of the superstructure of the crane carrier by means of thepin 35. The outer end of the arm 33 is connected to the toggle by meansof the pin A-l whose center is the anchor point A. The pin A-l is alsoconnected to the hydraulic piston-cylinder unit 35 as will hereinafterappear.

The hydraulic piston-cylinder unit 35 is comprised of a cylinder 36which is hinged at 37, the latter being connected to a fixed point onthe superstructure by means of a pin (not shown). Unit 35 also includesa piston 39 and an interconnecting piston rod 40 having an outer linkage41 which engages the pin A-l. The two fixed points of the above linkageare 35 and 37. The arm 33 has a longitudinal centerline that is colinearwith the line from A to II. Also, the unit 35 is so positioned that thecentral axis of the piston rod 40 is perpendicular to the line A-H.

Any force in the direction A-R will increase the pressure of thehydraulic fluid 42 which is contained within the cylinder 36. Thisincrease in pressure will be transferred by the conduit 43 to anysuitable measuring and control device (not shown) responsive to fluidpressure. These pressure-responsive devices would then preclude thefunction or functions which would overload the crane.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications, apart from those shown or suggested herein, maybe made within the spirit and scope of this invention.

For example, opening of the contact 23 could serve to remove powercompletely from the hoist motor and/or the boom lift motor, or circuitrycould be incorporated to merely disable the particular motor in thedirection in which it was moving at the time the overload was reached.In any event, it should be understood that additional controls will beprovided to operate any function in a manner to decrease the tiltingmoment after the contact 23 has been opened. Similar considerations holdtrue for the hydraulic embodiment.

What is claimed is:

1. In a hoisting apparatus having a superstructure, a boom pivotallysupported on said superstructure at a hinge point spaced from the centerof gravity of said hoisting apparatus, said boom being movable in avertical plane about said hinge point, a variable length boom supportmeans connected at one end to the free end of said boom and at its otherend to an anchor point adjacent said superstructure for moving said boominto different angular positions in said vertical plane, a rigidcantilever beam having a longitudinal centerline substantially colinearwith the line between said anchor point and said hinge point, said beambeing rigidly connected at one end to said superstructure adjacent saidhinge point the other end of said beam extending free from saidsuperstructure and being connected to said other end of said boomsupport means for constituting said anchoring point, hoisting meansconnected to the free end of said boom for supporting a load therefrom,and means mounted adjacent said anchor point end of said cantilever beamand independently thereof, responsive to the deflection of saidcantilever beam at the anchor point end thereof said means for sensingthe deflection of the rigid beam at the anchor point is an electricalswitch secured to the superstructure and positioned adjacent the anchorpoint end of the beam, said switch having operator means in contact withthe anchor point end of the beam whereby the switch contacts are closedwhen the deflection of the beam is less than a fixed predetermined valueand the switch contacts are opened when the deflection of said beamexceeds the predetermined value, the opening of said switch contactoperating to render inoperative the hoisting means to prevent furtherincrease of the pitching moment.

2. The improvement according to claim 1 including additional means alsoresponsive to the operating angle of said boom support at the anchorpoint end thereof to prevent the hoisting apparatus from lifting loadswhich would exceed the structural strength of said apparatus.

1. In a hoisting apparatus having a superstructure, a boom pivotallysupported on said superstructure at a hinge point spaced from the centerof gravity of said hoisting apparatus, said boom being movable in avertical plane about said hinge point, a variable length boom supportmeans connected at one end to the free end of said boom and at its otherend to an anchor point adjacent said superstructure for moving said boominto different angular positions in said vertical plane, a rigidcantilever beam having a longitudinal centerline substantially colinearwith the line between said anchor point and said hinge point, said beambeing rigidly connected at one end to said superstructure adjacent saidhinge point the other end of said beam extending free from saidsuperstructure and being connected to said other end of said boomsupport means for constituting said anchoring point, hoisting meansconnected to the free end of said boom for supporting a load therefrom,and means mounted adjacent said anchor point end of said cantilever beamand independently thereof, responsive to the deflection of saidcantilever beam at the anchor point end thereof said means for sensingthe deflection of the rigid beam at the anchor point is an electricalswitch secured to the superstructure and positioned adjacent the anchorpoint end of the beam, said switch having operator means in contact withthe anchor point End of the beam whereby the switch contacts are closedwhen the deflection of the beam is less than a fixed predetermined valueand the switch contacts are opened when the deflection of said beamexceeds the predetermined value, the opening of said switch contactoperating to render inoperative the hoisting means to prevent furtherincrease of the pitching moment.
 2. The improvement according to claim 1including additional means also responsive to the operating angle ofsaid boom support at the anchor point end thereof to prevent thehoisting apparatus from lifting loads which would exceed the structuralstrength of said apparatus.